Multiple choice

A person sold his watch for Rs. 75 and got a percentage profit equal to the cost price. The cost price of the watch was

  1. Rs. 60

  2. Rs. 50

  3. Rs. 40

  4. Rs. 70
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let CP = x. Profit % = x%. SP = CP + (x/100)*x = x + x^2/100 = 75. x^2 + 100x - 7500 = 0. (x + 150)(x - 50) = 0. Since CP > 0, x = 50.

AI explanation

Let the cost price be Rs. x; the problem states the profit percentage is also x. Using the formula Selling Price equals Cost Price plus Profit, we write 75 equals x plus x percent of x, which simplifies to 75 equals x plus x squared divided by 100. Solving the quadratic equation x squared plus 100x minus 7500 equals 0 gives x equals 50, making the cost price Rs. 50.

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